FYI: There is a null context manager: ExitStack().
On Sat, Oct 1, 2016 at 3:43 PM MRAB
On 2016-10-01 19:07, Neil Girdhar wrote:
I'm just throwing this idea out there to get feedback.
Sometimes, I want to conditionally enter a context manager. This simplest (afaik) way of doing that is:
with ExitStack() as stack: if condition: cm = stack.enter_context(cm_function()) suite()
I suggest a more compact notation:
with cm_function() as cm if condition: suite()
I'm not sure that this is possible within the grammar. (For some reason with with_expr contains '"as" expr' rather than '"as" NAME'?
I realize this comes up somewhat rarely. I use context managers a lot, and it comes up maybe 1 in 5k lines of code.
For some extensions of this notation, an else clause could bind a value to cm in the case that condition is false.
If you defined a null context manager, you could then write:
with (cm_function() if condition else cm_null()) as cm: suite()
Do you need 'cm' itself? Its type changes depending on the condition, so I don't see how it could be useful.
If it's not needed, then that shortens a little to:
with cm_function() if condition else cm_null(): suite()
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